Variable length compensating lever latch handle mechansim

ABSTRACT

A cam-lock handle to facilitate insertion, extraction, and holddown functions between a demountable equipment or device and its container or mounting base includes an operational variable pivot point assembly for the handle by means of which the mechanical advantage of the handle may be varied to optimize handle functions and ready adjustment for variations in equipment lengths is permitted.

United Mates Patent lnventor Casswell C. Hepker Cedar Rapids, Iowa Appl.No 887,014

Filed Dec. 22, 1969 Patented Nov. 9, 1971 Assignee Collins Radio CompanyCedar Rapids, Iowa VARiABLE LENGTH COMPENSATING LEVER LATCH HANDLEMECHANSIM 5 Claims, 9 Drawing Figs.

U.S. C1 312/320, 312/215 Int. Cl A47h88/00, A47b 95/02 Field of Search.Q 1. 312/320,

[56] References Cited UNITED STATES PATENTS 2,595,129 4/1952 Duguay3l2/320X 2,944,864 7/1960 Krivulkam. 312/320 3,039,837 6/1962 Poe312/320 3,189,938 6/1965 Saunders 312/320 UX Primary Examiner- Paul R.Gilliam Altorneys-Richard W4 Anderson and Robert]. Crawford PATENTEDuuv9 Ian 3,519,019

sum 1 [1F 5 FIG.!

INVENTOR. CASSWELL C. HEPKER AGENT PATENTEDuav 9 I97! 3,619,019

SHEET 2 OF 5 INVENTOR. CASSWELL ,CC HEP/(ER AGENT PATENTEDunv 9 IanKHANDLE MOVEMENT SHEET 3 OF 5 EQUIPMENT- MOVEMENT FIG.4

INVENTOR. CASSWELL C. HEP/(ER BY AGENT PATENTEUuuv 9 IBYI 3,619,019

SHEET [1F 5 33 [HANDLE MOVEMENT EQUIPMENT 0 MOVEMENT FIG. 5

INVENTOR. CASSWELL c. HEPKER AGENT PAIENTEnunv 9 nsn 3.619.019

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CASSWELL C. HEPKER v 421M AGENT VARIABLE LENGTH COMPENSATING LEVER LATCHHANDLE MECHANSKM This invention relates generally to latching mechanismsand more particularly to an improved latching mechanism for optimizinginsertion, extraction, and holddown capabilities of an equipmentcontained in a mounting base or rack.

More particularly the present invention relates to an improvement inlatching and holddown means for mounting and removal of an electronicequipment from a mounting base wherein numerous plug-jack electricalconnections are to be completed or disconnected as the equipment isinstalled or removed respectively.

Stringent requirements must be met for the mounting of airborne orotherwise mobile electronic assemblies in mounting racks or bases whereunits must be securely held and a solid mount maintained under theinfluence of a highly vibrational atmosphere and in the application ofvarious randomly directed shock forces.

Electrical interconnection between unit and mount may also entail themating and insertion of a multiplicity of electrical plugs and socketssuch that considerable frictional forces are encountered duringinsertion and extraction of the equipment from its mount.

Among numerous designs employed to facilitate mounting and holddown isthe cam-lock type of handle. The cam-lock handle aids insertion anddisconnect operations by providing a lever action between a cam lobe anda locking pin with mechanical advantage defined by dimensionalinterrelatiom ship between camming surface, the handle pivot point, andthe handle length.

Problems occur, however, with the cam-lock type of handle. Therelationship of the handle pivot point to the cam portion of the handleassembly is extremely critical to proper insertion-extraction andholddown capabilities of the handle. Inherent tolerances in equipmentlengths and the desirability and necessity for interchangeability ofunits in a permanently mounted rack or base are incompatible conditionsas concerns a cam-lock type of latching mechanism wherein the handlepivot point is fixed. In the absence of a means to adequately compensateor adjust for allowable tolerance in the length of units to be mounted,adjustment of a cam-lock type of assembly becomes difficult andunpredictable and may involve a time-consuming adjustment of the clevispin latch location with respect to the locking cam.

The object of the present invention is the provision of a cam-lock typeof handle assembly for cooperation with a fixed clevis or locking pinwhich incorporates novel adjustment means permitting movement of thehandle pivot point as required to adjust to variations in lengths ofequipments to be mounted or inserted.

A further object of the present invention is the provision of a novellength compensating lever latch handle mechanism for cooperation with afixed clevis pin latch assembly wherein the mechanical advantage of thelocking handle assembly is selectively variable on an operational basis,as contrasted to a preset basis.

A still further object of the present invention is the provision of alatching handle mechanism wherein the mechanical advantage of the deviceis selectively variable and may be readily adjustable to be greatest asthe equipment to be inserted nears maximum engatement where loads aregreatest.

Still another object of the present invention is the provision of alatching handle mechanism providing a selectively variable mechanicaladvantage extracting-inserting mechanism the use of which optimizedinsertion-extraction operations and which provides an optimized lockedholddown between inserted unit and mounting base respectively.

The present invention is featured in provision of a handle mechanismemploying first and second cam lobes for use in insertion and extractionoperations respectively operated by pivotable movement of a handlemechanism the pivot point of which may be selectively adjusted along aline substantially transverse of the longitudinal axis of the handlemember.

A further feature of the present invention is the provision of means forselectively increasing to a predetermined maximum value the forceexerted against the clevis or holddown pin by the locking cam lobe afterthe handle mechanism is in locked position.

These and other features and objects of the present invention willbecome apparent upon reading the following description with reference tothe accompanying drawings in which:

FIG. 1 is an exploded isometric view of a latching handle mechanism inaccordance with the present invention;

FIG. 2 is a side view of the latching handle mechanism in lockedposition;

FIG. 3 is a diagrammatic view of the variable mechanical advantagefeatures of a handle mechanism in accordance with the present invention;

FIGS. 4 and 5 are diagrammatic representations of relative positions ofhandle and locking pin illustrating insertion capabilities forrespective extreme pivot point adjustments;

FIG. 6 is a partial view illustrating a detented handlelocking featureof the present invention; and

FIGS. 7, 8, and 9 illustrate cam surface configuration and clevis pinshaping as employed in the present invention.

The cam-lock type of handle has been employed in the art as a convenientmeans for inserting and disconnecting equipments from mounting racks orreceptacles. The cam-lock of handle is essentially a lever applicationwhere the fulcrum is the pivot point of the handle and the mechanicaladvantage of the lever is defined by the point of application of arotational force on the handle and the lever arm distance between thepivot point and the point of engagement between the handle cammingsurface and a fixed locking pin or clevis.

In general, rotation of the cam-lock handle about its pivot axis,through the cooperative engagement of a camming hook with a holddown pincauses relative motion to be imparted between the equipment and itsmounting base, and the mechanical advantage of the handle determines theease and efficiency with which the injection and rejection function isaccomplished.

As mentioned above, considerable force must often be applied wheninserting electronic equipment into a rack due to the high frictionalforces imposed by the making" of multiple pin-socket connections.Alternatively, ejection and withdrawal of the equipment necessitates aconsiderable force to be applied to break the frictional holding forcesimposed by the pin-socket connections. The cam-lock type of handle, inaddition to providing a mechanical advantage for accomplishing theinsertion and ejection of equipments into mounting bases, provides, inits closed position, a holddown or lock means which might be generallycompared to that of a hook and a pin arrangement. The equipment is thusprotected from vibration and shock loads when the handle is in the lockposition.

The present invention uniquely accomplishes the known advantages of thecam-lock type of handle and provides a decided improvement in permittinga simple operator adjustment to adapt a locking handle assembly carriedon an equipment with a particular mounting base. As above described, itis oftentimes desired to interchange electronics equipments in a commonmounting base, and, due to tolerances in equipment length, thecam-locking handle may give rise to timeconsuming and unpredictablemisalignments between the handle and the base-mounted clevis pin latchassembly. The operation of a cam-lock handle is based on a relationshipof the handle pivot point to the cam portion of the handle assembly, andthis relationship is critical to the proper insertionextraction andholddown capabilities. The present invention provides a unique variablehandle pivot point such that the operator may easily adjust a givencam-lock handle assembly for optimized cooperation with a fixed clevisor locking pin on the equipment mounting base FIG. 1 illustrates ahandle mechanism in accordance with the present invention used to insertor extract a unit 10 from a cooperating mounting base 11. It is to berealized that the unit might be a piece of electronic gear in a boxedenclosure for attachment with a mounting base 11 or, alternately, unit10 might be the chassis of an electronic equipment and the mounting base11 comprise a fixed cabinetlike receptacle into which the equipment isto be inserted and extracted in drawerlike fashion. As illustrated inFIG. 1, the handle is shown in a locked position with respect to alocking pin or clevis member 13, and the equipment 10, with respect towhich the handle assembly is pivotably mounted, is illustrated as beingin a fully inserted relationship with respect to the mounting base 11.The locking pin 13 extends transversely through a slotted mounting dog12 which might be rigidly affixed to the front surface of the mountingbase 11 by means of a threaded hole 2 1 in the dog and a mounting bolt31. The slot accommodates the handle member into engaged cammingrelation with the locking pin 13. The handle 15 is illustrated as havinga longitudinal offset between the upper portion of the handle and thebottom camming extreme purely as a design expedient to provide a flusharrangement upon being placed in locked position; that is to say, thehandle shape conforms with the offset front panel shape of the unit 10to which it is attached such that, as better illustrated in FIG. 2,under a fully inserted and locked arrangement, the camming mechanismdoes not protrude ahead of the front face of the mounted equipment.

The handle 15 (referring again to FIG. 1) is pivotably mounted withrespect to first and second handle brackets 22 and 23. These bracketsare rigidly affixed, using mounting screws 34, to the front panel 10 ofthe unit to be mounted. The pin associated with the handle 15 is thusrotatably or pivotably mounted with respect to through-holes 29 and 30in the respective mounting brackets 22 and 23.

Referring to FIG. 2, and considering for the moment that the pivot pin20 associated with the handle 15 bears a fixed relationship with respectto the handle 15, it is seen that the handle 15, in conjunction with itspivot point 20 and the cooperative engagement between the locking pin 13and engaging point on camming surface 14a, form a lever arrangement. Themechanical advantage of the lever is defined by the relative lever armlength between the pivot point 20 and the point of application of forceby the operator on the upper portion of the handle, and the distancebetween the point of engagement of locking pin 13 and the cam 14a andthe pivot point. FIG. 2 illustrates the equipment 10 in fully mountedand locked relationship with the mounting base 11. It is noted that therelationship between the locking pin 13 and the cam surface providesboth a holddown and insertion force as regards the equipment 10 and themounting base 1 1.

If now one considers that the particular unit 10 of FIG. 2, which is tobe mounted on, or fully inserted within, a mounting means 11 has avariation in length along the insertion axis (a variation in equipmentdepth) different from optimum, the particular relationship of thelocking pin and camming surface and handle lock position will vary.Actually, even optimized tolerance as concerns the depths of theequipment to be mounted and the particular dimensions of the mountingbase (and thus location of the locking pin 13) may seriously affect theproper insertion/holddown capabilities of the handle.

Accordingly the present invention provides a means of varying theposition of the pivot pin 20 on the handle 15 along an axissubstantially transverse that of the longitudinal axis of the handle,whereby adjustment may be made for any particular unit/mounting-basepair to optimize the camming, hold down, and locking operations of aparticular handle with a given base. Tolerances which are normallyexpected in any manufacturing operation will then be accommodated. Inaddition, as will be further described, the movable handle pivot pointprovides a decided advantage in allowing the operator to control themechanical advantage of the handle lever so as to optimize the handlefor both extraction and insertion operations. A ready means is alsoprovided for applying added force between the locking surface andcamping pin after the mechanism is inserted in locked position to assureprotection from shock and vibration loads.

With reference to PEG. 1, the handle pivot pin 20 is seen to be carriedon a mounting member 25 which is free to translate along through-slot 26formed through the lower portion of handle 15. The slot axis isessentially transverse of the longitudinal axis of handle 15.

Pin-mounting member 25 is threadedly received on a lead screw 27 and isconstrained from rotation with respect to the handle due to itsconfinement within the slot 26. Rotation of the lead screw 27 by meansof knob 16, therefore, causes the pin-mounting member 25 to translatebetween predefined extreme positions within the slot 26, thus varyingthe position of the handle pivot pin 21) with respect to the handle.

Pivot pin 20 is rotatably received in mounting bracket through-holes 29and 30 and thus adjustments of the pivot pin position with respect tothe handle 15 adjusts the relationship of the handle and is cammingsurface with respect to the locking pin 13 which is rigidly affixed tothe mounting base 11. Although not shown in detail, it will beappreciated that the lead screw member 27 is mounted with the thrustwashers adjacent the handle 15 surfaces and provided with a tensionwasher and locking nut 28, such that the lead screw 27 is rotatablyretained in the handle assembly. The knob 16, by means of which thepivot pin adjustment is made, may be a torque knob, whereupon the knob16 rotates with respect to the lead screw 27 upon a predetermined torquebeing imposed by the operator.

The advantages of the variable pivot point may be appreciated byreference to FIG. 3 wherein the lower portion of the handle 15 includingthe pivot point adjustment and cam lobes is illustrated.

FIG. 3 illustrates the fixed locking pin 13 is locked relationship withrespect to the handle camming surface. The handle is formed with a frontcan lobe 14a and a rear cam lobe Mb. The hooklike cam arrangement isgenerally designated by reference numeral 14. The pivot pin 20 isillustrated in a first position 20 and a second position 20 representingthe respective extremes of adjustment effected by rotation of the torqueknob 16. With the pin in the position designated 20 in FIG. 3, a leverarm of length B is effected between the pin position 20 and the point ofengagement between locking pin 13 front cam lobe 14a.

With the pivot pin in position 20' a shorter level arm A is effected.Now considering that the operation grasps the upper portion of thehandle 15 at a given point, it is seen that the handle assembly, in itscooperative relationship between cam lobe 14a and locking pin 13,defines a lever of variable mechanical advantage. With the handle pivotpin at position 20, the B length lever arm between pivot pin and lockingpin defines a lever with less mechanical advantage than when the pivotpin is in position 20 with the shorter lever arm length A.

The torque knob 16 provides a convenient accessible adjustment of thismechanical advantage. With the handle pivot point at position 20, themechanical advantage of the handle is smaller because length B is largerand a predetermined handle movement will cause a proportionally largerincrement of equipment notion to the rear than with a pivot pin positionat point 20'. Thus the operator may adjust the pivot pin position bymeans of the torque knob 16 to move the equipment larger increments ofdistance to the rear with a smaller mechanical advantage at the initialpoint of insertion and then move the equipment smaller increments ofdistance to the rear with greater mechanical advantage by adjustment ofthe pivot point to position 20'. The advantage of this arrangement isthat the handle design permits an insertion process such that asequipment nears the maximum engagement to the rear and the loads aregreatest, the pivot point is nearest position 20' where the mechanicaladvantage is greatest. This advantage is illustrated functionally inFIGS. 4 and 5. FIG. 4 illustrates the pivot pin in position 20 tofacilitate greater increments of movement of equipment requiring smallerinsertion forces since the pivot pin position at point 20 provides asmall mechanical advantage. Conversely, FIG. 5 illustrates a pivot pinposition at point 20' to facilitate smaller increments of movement ofequipments with larger insertion forces, since a larger mechanicaladvantage is effected.

It is thus seen that the handle assembly may be advantageously used formating equipments with large injection forces by moving the handle pivotpoint to a setting such that the equipment is moved into its aft matedlocated in several successive bites or handle camming actions-that is tosay, if the equipment is difficult to inject, the pivot position can beset so that complete closure of the handle assembly moves the equipmentone small increment of the total distance required. The handle may thenbe released and another turn of the pivot point torque knob assemblymade, etc. until the complete engagement distance is accomplished. Eachmovement of the pivot can be as large or small as required and isdetermined only by how far the torque knob is rotated.

The handle assembly is locked by closing the handle. This closedrelationship is illustrated in H6. 2. As more particularly illustratedin FIG. 6, the handle might be formed with an inclined ramp surface 36to cooperate with a spring loaded ball member 37 such that during thefinal few degrees of handle closure, the spring-loading locking pin orball 37 rides up the inclined ramp 36 and drops into a spherical radiusdetent 34. With the handle now locked the torque knob 16 may be rotateduntil a present torque level is reached. When this point is reached,further rotation of the knob will slip the torque knob assembly. Therotation of this torque knob to achieve predetermined torque level afterhandle locking, allows an additional force to be exerted against theclevis or holddown pin 13 and prevents potentially damaging movement ofthe equipment due to vibration and shock loading.

The variable mechanical advantage feature of the handle assembly of thisinvention also provides an advantage in ejecting equipments in much thesame manner in which the equipment was injected, except the handle rearcam lobe 14a is used and pivot pin position provides the greatestmechanical advantage in that it provides the shorter level arm distancebetween the pivot pin location and the point of engagement of thelocking pin 13 and the cam surface.

After the equipment is ejected form its mounting means 11, the equipmenthandle 15 rotated into a carrying position by means of a lightly loadedleaf spring 18 (referring to FIGS. 1 and 2). The leafspring is guided ina spring guide slot 17.

The present invention is thus seen to provide an improved lever latchhandle mechanism by means ofwhich the mechanical advantage of the levermechanism may be advantageously adjusted to facilitate injection andremoval of equipments from mounting bases and by means of which asimple, readily accessible, adjustment for variation in tolerancesbetween equipments to be mounted and mounting bases may be effected and,finally, by means which the equipment, once locked in position, isprovided an added measure of safety against shock and vibration forces.

Although this invention has been described with respect to a particularembodiment thereof, it is not to be so limited as changes might be madetherein which fall within the scope of the invention as defined in theappended claims.

I claim:

1. A cam latching handle mechanism for facilitating translationalmovement between a first handle carrying member and a second membercarrying a locking pin member, said handle comprising arcuate camminglobe means operably engageable in hooklike fashion with said locking pinmember, said handle handle carrying a pivot pin extending transverse thedirection of said translational movement and received in first pinreceiving means fixed to said second member and second receiving meansassociated with said handle, whereby rotation of said handle memberabout said pivot pin axis effects a predetermined camming relationshipbetween said handle member and said locking pin member, and adjustmentmeans carried on said handle and in cooperative engagement with saidsecond receiving means for selectively varying the lever arm distancebetween said handle pivot pin axis and said locking pin member bytranslating the position of said second pivot pin receiving means alonga position axis which is substantially coextensive with the direction oftranslational movement between said first and second members when thelongitudinal axis of said handle is positioned substantially transversesaid direction of translational movement.

2. A mechanism as defined in claim ll wherein said arcuate camming lobemeans comprises first and second camming lobes within the confines ofwhich said locking pin member is receivable, each of said camming lobesbeing selectively positionable into camming relationship with saidlocking pin member upon rotation of said handle member about said pivotpin, said first and second camming lobes being formed such that rotationof said handle member in a first direction about said pivot pin effectsa communicating relationship between a first one of said camming lobesand said locking pin member to translate said first member in a firstdirection with respect to said second member and rotation of said handlemember in an opposite direction about said pivot pin effects acommunicating relationship between the second one of said camming lobesand said locking pin member to translate first member in the oppositedirection with respect to said second member.

3. A mechanism as defined in claim )1 wherein said pivot pin secondreceiving means comprises a substantially rectangular block slidablyconfined in a through-slot formed in said handle member said throughslot being coextensive with said pivot pin position axis, a lead screwmember received in threaded engagement with said block, the longitudinalaxis of said lead screw member being coextensive with said pivot pinposition axis and means for selectively rotating said lead screw withrespect to said handle member to effect translation of said block alongsaid position axis.

4. A mechanism as defined in claim 3 wherein said means for rotatingcomprises a torque knob affixed to an operator accessible end of saidlead screw member, the application of a predetermined torque to saidtorque knob effecting slippage between said knob and said lead screwmember.

5. A mechanism as defined in claim 1 wherein the face of said camminglobe means is formed with a locking pin engaging surface of arcuatecross section having a predetermined radius, said locking pin memberbeing formed with a decreasing radius from the transverse extremesthereof to the central portion to define a spherical radius less thanthe radius of said camming lobe means.

1. A cam latching handle mechanism for facilitating translationalmovement between a first handle carrying member and a second membercarrying a locking pin member, said handle comprising arcuate camminglobe means operably engageable in hooklike fashion with said locking pinmember, said handle handle carrying a pivot pin extending transverse thedirection of said translational movement and received in first pinreceiving means fixed to said second member and second receiving meansassociated with said handle, whereby rotation of said handle memberabout said pivot pin axis effects a predetermined camming relationshipbetween said handle member and said locking pin member, and adjustmentmeans carried on said handle and in cooperative engagement with saidsecond receiving means for selectively varying the lever arm distancebetween said handle pivot pin axis and said locking pin member bytranslating the position of said second pivot pin receiving means alonga position axis which is substantially coextensive with the direction oftranslational movement between said first and second members when thelongitudinal axis of said handle is positioned substantially transversesaid direction of translational movement.
 2. A mechanism as defined inclaim 1 wherein said arcuate camming lobe means comprises first andsecond camming lobes within the confines of which said locking pinmember is receivable, each of said camming lobes being selectivelypositionable into camming relationship with said locking pin member uponrotation of said handle member about said pivot pin, said first andsecond camming lobes being formed such that rotation of said handlemember in a first direction about said pivot pin effects a communicatingrelationship between a first one of said camming lobes and said lockingpin member to translate said first member in a first direction withrespect to said second member and rotation of said handle member in anopposite direction about said pivot pin effects a communicatingrelationship between the second one of said camming lobes and saidlocking pin member to translate first member in the opposite directionwith respect to said second member.
 3. A mechanism as defined in claim 1wherein said pivot pin second receiving means comprises a substantiallyrectangular block slidably confined in a through-slot formed in saidhandle member said through slot being coextensive with said pivot pinposition axis, a lead screw member received in threaded engagement withsaid block, the longitudinal axis of said lead screw member beingcoextensive with said pivot pin position axis and means for selectivelyrotating said lead screw with respect to said handle member to effecttranslation of said block along said position axis.
 4. A mechanism asdefined in claim 3 wherein said means for rotating comprises a torqueknob affixed to an operator accessible end of said lead screw member,the application of a predetermined torque to said torque kNob effectingslippage between said knob and said lead screw member.
 5. A mechanism asdefined in claim 1 wherein the face of said camming lobe means is formedwith a locking pin engaging surface of arcuate cross section having apredetermined radius, said locking pin member being formed with adecreasing radius from the transverse extremes thereof to the centralportion to define a spherical radius less than the radius of saidcamming lobe means.